Kennedy (U.S. Pat. No. 5,657,487) teaches the use of handovers to determine vehicles speed and the number of vehicles driving on a certain route. Kennedy does not supply a solution to the very common problem in metropolitan areas of the same handovers relating to several different routes. This invention also discloses an extremely expensive implementation requiring RF receivers spread over the covered area.
Kaplan et al (WO 02/03350 A1) discloses a low cost, totally passive method (monitoring the cellular network without sending any messages) to extract traffic information from any cellular network in every load stage possible, with minimal hardware elements and hence minimal system cost.
It specifically teaches an initial differentiation and screening method to assign handover sequences to a specific route. This method will work perfectly when there is only one road within a covered area of several cells. However Kaplan et al does not give a full solution to the real life handover sequences received in urban areas. If a vehicle travels several times through the same route it will rarely generate the exact same handover sequence, furthermore the resemblance to handover sequences derived by traveling on different routes may be significant.
The current invention extends the work done by Kaplan et al and teaches detailed methods that efficiently and accurately correlate handover chains to a specific route, and avoid ambiguous correlations.
Furthermore the current invention teaches a method to determine the handover location accuracy for handovers within these chains.
These two steps generate a reference database that serves as a basis to locate the route on which vehicles are driving and their speed.
In addition the current invention discloses a method to correlate cellular calls by vehicles in the operational stage with the reference database and extract speed data and incident reports in real time.